1. Field of the Invention
The present disclosure relates to an optical sensing unit, and more particularly, to an optical sensing unit, in which an infrared sensor module having a touch detection function is arranged on a display panel so as to achieve slimness of a device and to simplify casing elements, a display module and a display device using the optical sensing unit.
2. Discussion of the Related Art
In general, a touch screen is one of various schemes for constructing an interface between an information communication device using various displays and a user. The touch screen is an input unit, which can implement the interface between the user and a corresponding device to which the touch screen belongs when the user brings his/her finger or a pen into contact with the touch screen.
Touch screens allow the user to touch buttons displayed on a display device with his or her finger, and are interactively and intuitively operated by the user, such that anyone, regardless of age or sex, can easily use the touch screens. Therefore, the touch screens are becoming increasingly common and are being applied to a variety of fields including, for example, issuance machines for use in banks or public offices, various medical instruments, information guide systems for tourist attractions and organizations, traffic information systems, and the like.
The touch screens are classified into various types according to touch recognition methods employed, for example, a resistive type, a capacitive type, an ultrasonic wave type, an infrared type, and the like.
Although the above-mentioned types of touch screens have different advantages, an infrared-type touch screen is attracting public attention in consideration of minimization of pressure applied to a touch surface and convenience of arrangement.
Hereinafter, a conventional infrared-type touch screen assembly will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view illustrating the conventional infrared-type touch screen assembly and a liquid crystal display module connected therewith, and FIG. 2 is a perspective view illustrating the conventional infrared-type touch screen assembly and a tempered glass panel.
With reference to FIGS. 1 and 2, the conventional infrared-type touch screen assembly 20 is connected to the upper portion of the liquid crystal display module 15 including infrared sensor modules 15 and separate casing elements to fix the infrared sensor modules 15.
The touch screen assembly 20 includes the tempered glass panel 25 at a lower portion thereof which is not connected with the liquid crystal display module 10, thereby obtaining a touch input region. That is, the tempered glass panel 25 is located on the liquid crystal display module 10, and functions as a touch surface. Here, the lower surface of the tempered glass panel 25 contacts the upper surface of a top case of the liquid crystal display module 10.
The liquid crystal display module 10 includes a liquid crystal panel, an optical sheet and a backlight unit provided under the liquid crystal panel, and edges and lower surfaces of the liquid crystal panel, the optical sheet and the backlight unit are surrounded by casing elements, such as the top case and a bottom cover.
In FIG. 1, non-described reference numeral indicates supports used to support the liquid crystal display module 10.
In this case, the liquid crystal display device 10 including the infrared-type touch screen assembly 20 has a thickness greater than the sum total of the thicknesses of the casing elements of the touch screen assembly 20, the thickness of the tempered glass panel 25, and the thickness of the liquid crystal display module 10, thus being incapable of achieving slimness.
Further, the conventional infrared-type touch screen assembly 20 is formed separately from the liquid crystal display module 10. Therefore, a process for combining the touch screen assembly 20 and the liquid crystal display module 10 is required and, in order to implement a touch scheme, a process for collecting respective components and applying coordinates on the touch screen assembly 20 to the liquid crystal panel is required.
In addition, the above-mentioned infrared-type touch screen assembly 20 includes two infrared sensor modules. Therefore, the touch screen assembly 20 is located at the outside of the liquid crystal panel due to a dead zone, in which recognition of coordinates is difficult, on a line connecting the two infrared sensor modules. In this case, the outer region of a liquid crystal display device is increased, and thus the size of a bezel is increased.
Further, in the conventional infrared-type touch screen assembly 20 including the two infrared sensor modules, when two or more objects are placed on the touch surface, a real image corresponding to actual coordinates of the objects and a virtual image (ghost) in which the objects are not actually present but there is a measurable possibility that the objects are present are indistinguishable from each other, and thus multiple touch points cannot be precisely recognized.
The above-mentioned conventional infrared-type touch screen assembly has the following problems.
First, the touch screen assembly and the liquid crystal display module are formed separately from each other, and thus in order to achieve touch detection, it is necessary to fix the touch screen assembly and the liquid crystal display modules using different casing elements and then to connect the touch screen assembly and the liquid crystal display module. Further, since the tempered glass panel is located between the touch screen assembly and the liquid crystal display module to protect the liquid crystal display module from the casing elements of the touch screen assembly, the liquid crystal display device is thick and heavy.
Second, since the tempered glass panel is used as the touch surface, brightness of the liquid crystal panel is lowered due to reflection of light from the surface of the tempered glass panel, and reflection of indoor lighting appears on the screen.
Third, if two infrared sensor modules are used, a dead zone is generated, and thus it is difficult to narrow the width of the bezel and to recognize multiple touch points.
Fourth, since a touch control board to control the touch screen assembly and a board to control the liquid crystal panel are separately provided, an interface device to connect these boards is additionally required.